HG 1628 
,G62 
1885 
Copy 1 



Revised and Enlarged Edition, 

— .GM. „ 

u 7 °hort Methods 

HG 1628 

. G62 FOR— 

1885 

c p y j COMPUTING 

INTERESTED DMT 



100 BAYS INTEREST RULE. 






HENRY GOLDMAN*?,' 

Author of the ' ' Electric Detector, ' ' 

l JVew System for Detecting Errors in Trial Balances, 

" ioo Days Average Rule" Etc, 



8FCGJ£ 



^ 



Chicago, 

"FEB # 1805% 



&* 



t* 



right 1884, by HENRY GOLDMANN. 
4.11 Rights Reserved, 



♦ INTEREST*: 

Is a compensation given or received for the use 
of money; Principal, the money on which 
Interest is computed ; Rate of Interest, the 
number of per cent., and Amount, the sum of 
Principal and Interest. 

To find the Interest, if ihe time is given 
in days, the year figured at 360 days. 

100 DAYS INTEREST RULE. 

i. Divide the principal by one of the key 
numbers* of the following Table, according to 
the Rate. 

Note.— The units of the cents of the principal can 
always be omitted, their interest being ag a rule too small 
to cause any variation in the cents of the answer. This 
•Interest Rule, considering the tens of the cents of the 
principal, gives therefore more accurate results than other 
short methods, which either omit the cents entirely or 
correct the number of dollars. •» 

2. Add to or subtract from the result the 
part which the corresponding column indicates. 

Note. — The part has to be taken of the result of the 
division by the key number, and not of the principal. 
Where no part is given, the division by the key number 
is sufficient to arrive at the desired interest for I, 10 or 
ioo days. 

This sum or difference is the interest of the 
given principal, at the given rate, for i, io or 
ioo days, according to how many places to the 
left the decimal point is removed: i place for 
ioo days, 2 places for 10 days and 3 places foi 
1 day. 



* The key numbers for the most frequent rates can be easily remem- 
bered, being the result of 36 divided by the given rate. 



LIBRARY OF CONGRESS 



To gain on the c 



5 %, divide the same 


by 20 


IO " 


Li 


LL 


10 


i 2 i" 


ll 


LL 


8 


15 " 


ll 


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20 


20 '• 


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25 " 


a 


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4, 


30 " 


1: 


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33^" 


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3, 


35 " 


ll 


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20, 


40 '< 


ll 


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60 " 


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66%" 


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70 " 


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10, 


80 " 


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LL 


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90 '• 


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LL 


10. 



027 331 583 4 

antt multiply the result by 2 1 
" "11 



To gain of the selling price : 

5 X divide the cost price by 1 9, and multiply the 
9, « 

/ J 

17, " 



IO " 


12^" 


15 " 


20 '< 


25 " 
30 " 

33^" 


35 ; < 
40 " 


45 " 
50 " 
60 " 


66%" 


70 " 
80 " 



90 



3, 
7, 
2, 
13, 
6, 

1, 

4, 
1, 

3, 
2, 
1. 



14 


23 


LL 


12 


LL- 


5 


LL 


13 


LL 


4 


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27 


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•14 


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29 


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15 


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16 


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5 


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17 


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18 


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x 9 


result by 20 


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10 


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JQ 



^INTEREST 



<T 



Is a compensation given or received for the use 
of money ; Principal, the money on which 
Interest is computed ; Rate of Interest, the 
number of per cent., and Amount, the sum o 
Principal and Interest. 

To find the Interest, if ihe time is giver 
in days, the year figured at 360 days. 

100 DAYS INTEREST RULE. 

i. Divide the principal by one of the ke^ 
numbers* of the following Table, according t< 
the Rate. 

Note. — The units of the cents of the principal cai 
always be omitted, their interest being a£ a rule too smal 
to cause any variation in the cents of the answer. Thi 
• Interest Rule, considering the tens of the cents of th< 
principal; gives therefore more accurate results than othe 
short methods, which either omit the cents entirely o 
correct the number of dollars. •* 

2. Add to or subtract from the result the 
part which the corresponding column indicates 

NOTE.— The part has to be taken of the result of tin 
division by the key number, and not of the principal 
Where no part is given, the division by the key numbe 
is sufficient to arrive at the desired interest for I, io o 
ioo days. 

This sum or difference is the interest of the 
given principal, at the given rate, for i, io o: 
ioo days, according to how many places to th( 
left the decimal point is removed: i place foi 
ioo days, 2 places for 10 days and 3 places fo 
1 day. 

* The key numbers for the mdst frequent rates can be easily remem 
bered, being the result of 36 divided by the given rate. 



■^INTEREST*. J 

100 DAYS INTEREST RULE. 


TABLE. 


-4- 










SHORT INTEREST RULE. 




1 » 


i 






mi"" 


M 


<&£&. 













100 DAYS INTEREST RULE. 






■{1 



7.3 PER CENT. 



EST ON ENGLISH MONEY. 



— 3— 

To obtain the interest for any given number 
of days, multiply the hundreds, tens or units of 
days by the corresponding amount of interest, 
and add these products together. 



Note. — If the given number of days is between 90 and 100, it 
more practical to deduct from the interest for too days as many times 
the interest for 1 day as there are days less. 



TABLE. 



RATE. 


Key Number. 


PART 


Per cent. 


Divide by 
l8 


to be added. 


to be deducted. 


I 
2 






3 

4 

5 


12 
12 

9 
8 
6 


One-sixth 


One -sixth 
One- twelfth. 


SV2 

6 

b% 

7 

1% 
8 

8^ 
9 , 
9 l A 

10 

11 


6 
6 
6 
6 
6 
6 
4 
4 
4 
3 
3 


One-twelfth. 

One-sixth. 

One-quarter. 

One-third. 


One- eighteenth. 


One -eighteenth 


One-sixth. 
One-twelfth. 


12 


3 







To compute the interest for rates, which are 
not given in this Table, add or deduct the 
proper aliquot parts of the interest at 2. 3, 4, 4^, 
6, 9 or 12%. For instance: To obtain the 
interest for 4|%, find the interest for $\% and 
add its eighteenth ( x 8 ) part. 



Xo*i27= 



— 4— 

EXAMPLES. 

$763. — . at 6 % for 93 days. 

1 2 7 1 =Interest for 100 days. 

89 = " " - 7 " 



Answer: $11*82 =Interest for 93 days. 
$136.43 at 5 % for 113 days. 

6)136-43 
2*27 
s "37 



Xi*90= T.90 =Interest for 100 days. 

Xo* I 9= x 9 = " " IO " 

Xo'o2= 6= " " 3 " 

Answer : $2*15 =Int-erest for 113 days. 



SHORT INTEREST RULE. 

For the following rates and the corresponding 
umber of days the interest is found without any 
alculation, by simply removing the decimal 
oint of the principal two places to the left. 



4 

2 

4 
3 
4 
4 



,360 days. 



, 240 
.180 

.144 

. 120 

• 9° 
, 80 

, 72 



7*" 

8 " 


... 60 days 

...48 - 
....45 " 


9 " 

TO " 


40 " 

....36 "" 


12 '• 


....30 " 


15 " 
18 " 


....24 " 
20 " 



Revised and Enlarged Edition, 

"hort Methods 

Copy i COMPUTING 

i INTERESTED DISCOUNT 

100 BAYS INTEREST RULE. 

i v^.,, } , 


To find the interest if the time is given 
m months, or months and days. 


PRESENT WORTH, 


COMPOUND INTEREST 








^IS : 


-OISCOUNT*— 

- 'S 8 S 


5 8 ° a 


D LOSS. 




ilWiiiiiiiifiiii ' 

-"■■■■ 027 331 583 4 


TABLE 








-«#^§e»- 



_ 4 _ 

EXAMPLES. 

$763. — . at 6 % for 93 days. 

6)76yoo_ 

127 1 =Interest for 100 days. 
Xo-i27= 89 = " "- 7 " 

Answer: $11*82 =Interest for 93 days. 

2. $136.43 at 5 % for 113 days. 

6)i3 6 *43 



— /6 



2*27 

'37 



Xi"9°= 
Xo-i9= 

Xo*02 = 

Answer : $2*15 =Int-erest for 113 days. 



T.90 =Interest for 100 days. 
19 = " " 10 " 

6 = " " 3 " 



SHORT INTEREST RULE. 

For the following rates and the corresponding 
umber of days the interest is found without any 
U dilation, by simply removing the decimal 
Dint of the principal two places to the left. 



1 

2 
2^ 

3 
4 

4i 

5 



360 


days. 


/o . . 


240 


a 


7 2 


180 


a 


8 " .. 


144 


a 


9 " ."■ 


120 


a 


10 


90 


' ; 


12 


80 


a 


i5 " . 


72 


a 


18 " ., 



. . 60 days. 

..48 " 

••45 " 

. . 40 " 

..36 " 

••30 " 

..24 " 

..20 " 



— 9— 
EXAMPLE. 



$360.00 for 16 days ■< $' 

72.18 " 29 " i J * 



Find the interest on the following items at th 
rate of 6%. 

.60 

.16 

•44 

65 

1293 6 " 34 " | 3 '^ 

87.50 " 80 " 7.00 

(4.03 
40.29 " 112 " < 40 

( 3 

23.76 

1. 6) 2376 

Answer: $3*96, Interest; the year figured a 
360 days. 

2. 2)2*376 

1-188 

3 
3'5 6 

Answer: $3.91, Interest; the year figured 2 
365 days. 

INTEREST ON ENGLISH MONEY. 

Reduce the s. and d. to decimals of £1, (se 
" New Systems for Proving Calculations wit 
English Currency,') and proceed according t 
the Rules for computing interest on America 
money, with the deviation that one more decim 
should be figured. The decimals of the ans\v< 
must be resolved again into s. and d. accordir 
to the given method. 



LIBRARY OF CONGRESS 



027 331 583 4 



